1. Field of the Invention
The present invention relates to a rolling bearing fixing device for fixing rolling bearings to a housing thereof, and a bearing unit in which a plurality of rolling bearings are fitted and inserted into a housing.
2. Description of Related Art
In recent years, transmissions for vehicles have been made smaller and smaller in line with downsizing of vehicles. For this reason, recently, when fixing a rolling bearing for rotatably supporting a rotation shaft of a transmission, there are known methods such as a stepped portion being provided at the outer ring side of a rolling bearing and the rolling bearing being fixed at a housing by using a retainer plate to shorten the entire length of the transmission.
As a known rolling bearing fixing device using this method, proposed are, a rolling bearing fixing device in which an outer ring is internally fitted to a housing and an axial one end surface of the outer ring is locked at a fixing plate fixed to the housing for restricting an axial movement of the rolling bearing (for example, U.S. Pat. No. 5,788,210); and a rolling bearing fixing device in which a groove portion is provided on an outer circumferential surface of an outer ring and a fixing plate is press-fitted to the groove portion for restricting the axial movement of the rolling bearing (for example, DE 20019278U1).
In addition, in attempt to downsize weight saving of a transmission, it is demanded that a plurality of axes are located as close to each other as possible. In light of this, a bearing unit in which a plurality of rolling bearings to support these axes are fitted and inserted into the housing adjacently to each other has been proposed (For example, refer to Japanese Unexamined Patent Publication JP-A-11-270568).
Further, as shown in FIG. 14 through FIG. 16, a bearing unit 201 disclosed in JP-A-11-270568 has two rolling bearings 210 and a housing 220 supporting both the bearings 210 so as to be adjacent to each other while having a clearance between their outer rings 211. The rolling bearings 210 are fitted and inserted into accommodation holes 221 formed in the housing 220, respectively. A substantially cylindrical wall portion 222 that forms accommodation holes 221 of the housing 220 is formed to be partially fused so as to locate the rolling bearings 210 adjacently to each other. The housing 220 having such a shaped wall portion 222 is formed by deep drawing process of a metal plate.
Further, a rolling bearing that prevents an outer ring of a rolling bearing attached to a housing from creeping, that is, prevents the outer ring from slipping in the rotation direction in the accommodation hole of the housing has been proposed (For example, Japanese Utility Model Unexamined Publication JP-UM-A-52-152932).
As shown in FIG. 17 and FIG. 18, a rolling bearing disclosed in the JP-UM-A-52-152932 has a notched portion 114 formed on an outer circumferential surface 112 at an axial end portion of the outer ring 111. A substantially circular accommodation hole 121 into which the rolling bearing 110 is fitted and inserted is formed in the housing 120. This accommodation hole 121 has a projecting portion 122 which corresponds to the notched portion 114 of the outer ring 111. The rolling bearing 110 is fitted and inserted into the accommodation hole 121 by engaging the notched portion 114 of the outer ring 111 with the projecting portion 122 of the accommodation hole 121 of the housing 120. Accordingly, because the rolling bearing 110 is fixed in the housing 120 by engaging the notched portion 114 with the projecting portion 122 of the accommodation hole 121, the outer ring 111 is prevented from rotating in the accommodation hole 121.
However, in the rolling bearing fixing device according to U.S. Pat. No. 5,788,210 described above, since it is necessary to lengthen the axial length of the housing in order to assemble a rolling bearing, the transmission may become large in size. In addition, when the housing is made of aluminum, if attempting to shorten the axial length of the housing, there is a fear that the housing will be damaged due to a shortage of the strength. Further, in the rolling bearing fixing device according to DE20019278U1 described above, since it is necessary to press-fit and fix the fixing plate in the grooved portion of the outer ring, assembling efficiency is not satisfactory.
In the bearing unit 201 disclosed in the JP-A-11-270568, the housing 220 is formed by deep drawing process of the metal plate. However, according thereto, as shown in FIGS. 7 and 8, on an area 223 where the wall portions 222, which form accommodation hole 221, fused with each other and the rolling bearings 210 most closely approach each other, no material is remained. That is, because the accommodation holes 221 communicate with each other at the area 223, an area which is not supported by the housing 220 is generated on the outer ring 211 of the rolling bearing 210. For this reason, uneven load is applied onto the outer ring 211 of the rolling bearing 210 to cause a deformation of the outer ring 211. Thus, there is a fear that the outer ring is damaged. Further, since force for fixing the outer ring 211 is lowered, there is a fear that creep of the outer ring 211 occurs.
The rolling bearing 110 disclosed in, for example, the JP-UM-A-52-152932 is effective to prevent the outer ring from creeping. However, in the JP-UM-A-52-152932, both end surfaces of the outer ring 111 are held by the housing 120 and a cover 123 attached to the housing 120 in the axial direction, whereby the axial displacement of the rolling bearing 110 is restricted. In this case, axial dimensions the bearing unit including the rolling bearing 110, the housing 120 and the cover 123 are apt to become large and this configuration is not suitable for downsizing.